This invention relates to a method for laser-induced metallization on semiconductor substrates.
While it is possible to produce high resolution patterns by deposition techniques wherein masking is employed to delineate the pattern, such plating processes require multiple steps. It is necessary to employ a photoresist to mask the surface, to selectively expose the photoresist mask, to plate the surface and finally, to strip the mask. This process is a multistep process.
It is known to expose an electroless plating solution to a high intensity light source to enhance the plating rate. While this technique increases the plating rate, it is not well suited for preferentially plating patterns since there will be mixing of the activated solution with the nonactivated solution. This mixing will reduce the resolution of any resulting pattern.
It is also known to coat a surface to be plated with a sensitizing solution. The coated surface is exposed to light to form a catalytic layer capable of catalyzing the deposition of metal thereon from an electroless metal deposition solution. Again, this technique suffers from the limitation of being a multistep process and requires a light activated catalytic layer.
Ridenour et al, in U.S. Pat. No. 3,762,938, describe a process for depositing elemental metallic coatings on solid substrates which comprises forming a hydride of the metal to be deposited in situ on a substrate and subjecting the metal hydride to sufficient energy to deposit the elemental form of the metal on the substrate. The source of energy may be heat, actinic light or high energy radiation, such as electron bombardment. This technique suffers from being a multistep process.
Beauchamp et al, U.S. Pat. No. 4,324,854, describe a process for depositing a thin film of material such as a metal onto a substrate through photodissociation of a gaseous compound capable of electron capture dissociation, such as a metal carbonyl. Deutsch et al, U.S. Pat. No. 4,340,617, describe a process for depositing a thin film of material such as metal onto a substrate through laser induced photolytic decomposition of a gaseous compound, such as organo-metallics, metal carbonyls, metal halides and the like. These techniques suffer from the relative complexity of the apparatus required.
Blum et al, U.S. Pat. No. 4,239,789, describe a process for depositing a metal onto a workpiece comprising a thin layer of metal or an active layer of solution such as palladium chloride which comprises contacting the surface with an electroless plating solution and directing an energy beam onto the workpiece to locally heat the surface to promote enhanced plating. Kulynych et al, U.S. Pat. No. 4,349,583, describe a similar process wherein the plating solution does not contain a reducing agent. These patents do not address the plating of metals onto non-metallic surfaces.
Accordingly, it is an object of the present invention to provide a method for selectively plating onto the surface of a non-metallic workpiece.
Other objects and advantages of the present invention will be apparent to those skilled in the art from a reading of the following description of the invention.